Power knife grinder for a forage harvester capable of grinding first and second bevels on the knives of the forage harvester cutterhead

ABSTRACT

A powered knife grinder carried by a forage harvester and operable in one mode of operation to grind a first bevel on the forage harvester knives, and operable in a second mode of operation to grind a second bevel on each of the knives. The knife grinder includes a rotary abrasive member which is connected with the drive line to the forage harvester cutterhead when the knives are to be ground. During normal operation of the forage harvester when cutting crops the drive to the grinding means is disconnected. When grinding the first bevel on the forage harvester both the grinding means and the cutterhead are rotated, the grinding means being moved back and forth across the width of the cutterhead to grind the first bevel. During grinding of the second bevel, the drive to the cutterhead is disconnected, however, the drive to the grinding means is maintained and the grinding means is positioned along a radial inner surface of each knife to grind the second bevel. To facilitate the grinding of the second bevel, the cutterhead is spring biased against guide means carried by the grinding means to maintain each knife in its desired position with respect to the grinding means as the grinding means is moved back and forth across the width of the cutterhead during the grinding of the second bevel.

United States Patent [191 Wagstaff et a].

POWER KNIFE GRINDER FOR A FORAGE HARVESTER CAPABLE OF GRINDING FIRST ANDSECOND BEVELS ON THE KNIVES OF THE FORAGE HARVESTER CUTTERHEADlnventors: Robert A. Wagstaff; Thomas W.

Waldrop, both of New Holland, Pa.

Assigneez Sperry Rand Corporation, New

Holland, Pa.

Filed: Jan. 4, 1972 Appl. No.: 215,615

Related US. Application Data Continuation-impart of Ser. No. 183,392,Sept. 24, 1971.

US. Cl 51/249, 51/288, 51/327 Int. Cl .l B24b 3/42, B24b 1/00 Field ofSearch..... 51/246, 247, 249, 326, 327,

References Cited UNITED STATES PATENTS [4 1 Feb. 26, 1974 3,479,77611/1969 Berg 51/249 Primary Examiner0thell M. Simpson Attorney, Agent,or Firm-Frank A. Seemar; John R. Flanagan; Joseph Brown [5 7] ABSTRACT Apowered knife grinder carried by a forage harvester and operable in onemode of operation to grind a first bevel on the forage harvester knives,and operable in a second mode of operation to grind a second bevel oneach of the knives. The knife grinder includes a rotary abrasive memberwhich is connected with the drive line to the forage harvestercutterhead when the knives are to be ground. During normal operation ofthe forage harvester when cutting crops the drive to the grinding meansis disconnected. When grinding thefirst bevel on the forage harvesterboth the grinding means and the cutterhead are rotated, the grindingmeans being moved back and forth across the width of the cutterhead togrind the first bevel. During grinding of the second bevel, the drive tothe cutterhead is disconnected, however, the drive to the grinding meansis maintained and the grinding means is positioned along a radial innersurface of each knife to grind the second bevel. To facilitate thegrinding of the second bevel, the cutterhead is spring biased againstguide means carried by the grinding means to maintain each knife in itsdesired position with respect to the grinding means as the grindingmeans is moved back and forth across the width of the cutterhead duringthe grinding of the second bevel. v

30 Claims, 12 Drawing Figures PATENTEUFEBZB I974 SHEET 1 [IF 5PATENTEDFE 26 19m SHEET 3 [IF 5 PATENTED FEB 2 6 I974 sum u 0F 5PATENTEDFEB25 I974 sum 5 OF 5 FIG H v CROSS REFERENCE TO RELATEDAPPLICATION This application is a continuation-in-part of abandoned US.application Ser. No. 183,392 filed Sept. 24, 1971, and entitled ForageHarvester Knife Sharpener with a Power Driven Abrasive Wheel and KnifePositioning Guide Pins for Grinding Relief Bevels.

This application also relates to the following patent applications allassigned to the same assignee as this application:

US. application Ser. No. 138,510 filed Apr. 29, 1971, and entitledReverse Drive for a Forage Harvester Cutting Reel now US. Pat. No.3,678,772.

US. application Ser. No. 138,540 filed Apr. 29, 1971, and entitledForage Harvester, now US. Pat. No. 3,730,441 and US. application Ser.No. 183,391 filed Sept. 24, 1971 and entitled Forage Harvester KnifeSharpener with a Rotary Abrasive Wheel.

FIELD OF THE INVENTION This invention relates generally to agriculturalma- BACKGROUND OF THE INVENTION In order to maintain the operatingefficiency of a forage harvester of the type having a rotatablecutterhead with knives spaced on the periphery thereof, the knivescooperating with the shear bar to cut crop material, it is necessary tokeep the knives sharp. It has been generally conventional to providesuch a forage harvester with an abrasive stone'which cooperates with thecutterhead during rotation thereof to grind the outer peripheryof theknives. This grinding produces what is known as a first bevel. However,as the length of the first bevel increases the efficency of thecutterhead will go down even though a sharp edge is fonned on saidknife. This is due to the heel portion of the first bevel draggingagainst crop material in the forage harvester. It haslong beenrecognized that forage harvester effi-' ciency can be improved byforming a second bevel on the knife edge which extends at an angle tothe first bevel to reduce the length of the heel of the first bevel.Thus, it is customary toinstall as original equipment knives havingfirst and second bevels. During the normal operation of mostcommercially available forage harvesters the first bevel is periodicallyresharpened to maintain a good cutting edge. However, as the heelbecomes progressively longer it is then necessary to regrind the secondbevel. In the past this has been done in a variety of ways. One methodinvolves holding the cutterhead in place within the machine and grindingthe second bevel by hand. This method is generally not to satisfactory.Anothermethod involves removing the knives from the machine and thengrinding the second bevel when the knives are removed from the machine.While a satisfactory second bevel can be reformed in this manner it is avery time constuming task and also involves careful repositioning of theknives in the machine after they have been rebeveled. Recently anattachment has been made available for forage harvesters which consistsof an electrically driven grinding wheel which is mounted on the forageharvester and advanced back and forth across the length of each knife toregrind the second bevel. While this attachment operates in a generallysatisfactory manner it is relatively expensive as it requires aduplication of parts. In other words, a separate power source and aseparate grinding means is required for grinding the second bevel.

SUMMARY AND OBJECTS OF THE INVENTION According to the principles of thisinvention a method and apparatus is provided for grinding first andsecond bevels on the knives of a forage harvester cutterhead while theknives are mounted on the cutterhead with a single grinding meansmounted on the forage harvester whereby the knives on the cutterhead canhave a first bevel ground thereon during rotation of the cutterhead byadvancing the grinding means into engagement with the radial outerperiphery of the rotating cutterhead and moving the grinding means backand forth along the length of the knives until the first bevel issatisfactorily sharpened and then disposing the cutterhead in a freewheeling mode and biasing each individual knife in turn against guidepins while moving the grinding means, which is disposed into engagementwith the knives behind the first bevel back and forth to satisfactorilygrind a second bevel, this step being repeated for each of the knives ofthe cutterhead.

The principal object of this invention is to provide a knife grinder fora forage harvester which is operable in one mode of operation to grindthe first bevel on the knives of the forage harvester, while the knivesare mounted on the cutterhead of the forage harvester, and, in a secondmode of operation to grind the second bevel on the knives, while theknives are still mounted on the cutterhead of the forage harvester.

It is a further objectof this invention to provide a knife grinder ofthe type referred to in the preceding paragraph which utilizes only asingle grinding means for grinding both first and second bevels.

It is another object of this invention to provide a grinding means forgrinding first and second bevels of the knives in a forage harvesterwhen the knives are mounted on the forage harvester cutterhead, theknife grinder utilizing a single source of power.

It is a further object of this invention to provide a novel method ofgrinding first and second bevels on the knives of a forage harvester.

It is a further object of this invention to position the knife andabrasive wheel in a substantially constant relation to one another overa range of diameters of the abrasive wheel and over a range of diametersof the cutting head.

Another object of this invention is to provide means on the knifesharpener that engages the cutting edge of These and other objectsandadvantages of this invention will be apparent to those skilled in theart after a consideration of the following detailed description taken inconjunction with the accompanying drawings,

in which the preferred form of this invention is illustrated.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a forage harvesteremploying the power knife grinder of this invention, this figure, aswell as the other figures of the drawings, being drawn generally toscale.

FIG. 2 is a right side view of a portion of the forage harvester showinin FIG. 1.

FIG. 3 is an enlarged plan view of a portion of the forage harvestershown in FIG. 1, this view illustrating the power knife sharpenerdisposed in position for grinding a second bevel on one of the knives ofthe forage harvester cutterhead.

FIG. 4 is a rearrview of a portion of FIG. 3 illustrating the means bywhich the power knife grinder can be adjusted towards and away from theperiphery of the cutterhead.

FIG. 5 illustrates a portion of the adjusting means shown in FIG. 4.

FIG. 6 illustrates the manner in which the guide pins, carried by theknife grinder, are held in their operative and inoperative positions.

FIG. 7 illustrates the cross section of one of the knives of thecutterhead and more clearly illustrates the shape of the first andsecond bevels.

FIG. 8 illustrates the manner in which the power knife grinder isdisposed when cutting the first level on the knives of the cutterhead.

FIG. 9 illustrates the manner in which the power knife grinder isdisposed when cutting the second bevel on one of the knives of theforage harvester cutterhead.

FIGS. l0, l1 and 12 represent the power knife grinder in, respectively,an inoperative position, in position to cut a first bevel, and in theposition wherein it is cutting a second bevel on one of the knives.

These viewes also illustrate the disposition of various drives, etc.,when the knife grinder is disposed in the various positions.

DETAILED DESCRIPTION In the following description right-hand andleft-hand reference is determined by standing to the rear of the forageharvester and facing in the direction of travel.

IN GENERAL Referring first to FIG. 1, a drawn forage harvester,indicated generally at is shown in plan view. The forage harvester has amain frame including a transversely extending frame member 12,fore-and-aft extending side sheets 14, 16, a rear transverse framemember 18 and a forwardly extending hitch frame indicated generally at20. The frame, which has only been partially illustrated and described,is supported upon left and right ground engaging wheels 22, 24,respectively. The hitch frame 20 includes a forwardly extending subframe26 and a swingable hitch bar 28 which is adapted to be secured to thedraw bar 30 of a tractor in a conventional manner. The tractor, of whichthe draw bar is a part, is a conventional'farm tractor and is providedwith a power takeoff shaft 32. The power takeoff shaft 34 of the forageharvester 10 is adapted to be connected to the power takeoff shaft 32 ina convention manner. As can be seen from the foregoing, when the forageharvester 10 is secured to the tractor, the forage harvester can bepropelled in a forward direction indicated by the arrow 36) by thetractor, the tractor also supplying power to the various operativecomponents of the forage harvester through the power takeoff shaft 32 ofthe tractor.

Mounted on the frame of the forage harvester is a cutterhead, indicatedgenerally at 38, and a blower, indicated generally at 40. Extendingbetween the cutter head 38 and the blower 40 is an auger trough 42through which material cut by the cutterhead may be conveyed to theblower 40. A gearbox 44 is also mounted on the forage harvester frame.The power takeoff line 34 extends forwardly from the gearbox 44 to thetractor power takeoff shaft 32, the power takeoff line being disposedbeneath a power line shield 46. The gearbox is provided with two outputshafts, one of them, 48, being connected directly to the fan within theblower 40. The other output shaft 50 is interconnected with the drivemeans which rotates the forage harvester cutterhead and which alsosupplies power to various other operative components of the forageharvester and to the power knife grinder in a manner more fully setforth below. It should however be noted at this point thatthe outputshaft 50 is connected to a main drive shaft 52 through a doubleuniversal joint drive line 54. A belt drive 56 extends forwardly fromsheave 58 mounted on the main drive shaft 52 to a sheave 60 carried oninput shaft 62 of gearbox 64. The gearbox 64 in turn has an output whichis connectable to various forage harvester attachments which are adaptedto be mounted on the forage harvester frame forwardly of the cutterhead38. These attachments customarily include those devices which deliverthe crop material to the forage harvester cutterhead, the crop materialbeing conveyed rearwardly by upperand lower feed rolls 66, 68,respectively (FIG. 2) over a shear bar 70. As the cutterhead is causedto rotate in a forward direction the knives 72 carried by the cutterheadwill engage the crop material being conveyed rearwardly over the shearbar and cut this material into relatively small pieces.

To maintain cutting efficiency of the forage harvester it is necessaryto maintain the knives 72 in a sharpened condition. In order to sharpenthe knives a powered knife grinder,indicated generally at 74, is mountedon the left and right side sheets 14, 16 of the frame. According to theprinciples of this invention, the knife grinder 74 may be disposed ineither a first grinding position for cutting a first bevel 76 (FIG. 7)on a knife, or in a second grinding position for cutting a second bevel78 on the knife. Alternatively, the power knife grinder may be disposedin an inoperative mode while the cutterhead is being rotated to cutforage crops conveyed rearwardly over the shear bar 70.

The powered knife grinder includes: grinding means, indicated generallyat 79, the grinding means including a rotatable abrasive memberdisconnectable drive means, indicated generally at 82, between thecutterhead drive means 52 and the grinding means 79; means, indicatedgenerally at 84, operable to move the grinding means 79 towards and awayfrom the cutterhead 38; and means, indicated generally at 86,operacutterhead.

. ble to move the grinding means back and forth along the width of thecutterhead.

Before describing all the constructional details of the powered knifegrinder, a brief summary of its different modes of operation will begiven.

SUMMARY OF OPERATION Referring to FIG. 10, the powered knife grinder isshown in this figure in an inoperative position. In this position therotatable abrasive wheel 80 is disposed away from the outer radialperiphery of the cutterhead 38 and it is customary not to drive thegrinder in this position. In this mode of operation the main drive shaft52 is connected to the cutterhead drive shaft 88 through a clutch,indicated generally at 90, the clutch being disposed in its normalclutching position. The main drive shaft 52 will be rotated in thedirection indicated by the arrow 91, and the'cutterhead will also berotated in this direction, which is referred to as its forward directionof rotation. As the cutterhead rotates in this direction the leading orcutting edge of the knives 72 will cut crop material conveyed rearwardlyover the shear bar 70.

If it is desired to grind the first bevel 76 on the knives of the forageharvester, the first bevel lying in the circumference of the cutterhead,the grinding wheel 80 is moved from its inoperative shown in FIG. to itfirst grinding position shown in FIG. 11 by the means 84 operable tomove the grinding means towards and away from the cutterhead. Thisdisconnectable drive means 82 between the cutterhead drive means and therotatable abrasive structure 80 is disposed in its connected position.In this position the grinding means drive belt 92 is moved from itsdisconnected or storage position, shown in FIG. 10, to its drivingposition wherein it is disposed over a sheave 94 on the main drive shaft52 and a sheave 96 operatively interconnected with a flexible drive line98. The rotary abrasive stone 80 is in turn connected with the flexibledrive line 98 in a manner which will be more fully brought out below.When the grinding means 79 before has been moved into its first grindingposition by the moving means 84, it is thennecessary to rotate thecutterhead in order to grind the first bevel. The cutterhead may berotated in either a forward direction, or, preferably, in a reverse Whengrinding the second bevel the grinding means is disposed in the mannerillustrated in FIG. 12. In this mode of on the second bevel is groundone one knife at a time. Thus, it is essential that the drives to thecutterhead be disconnected. Accordingly, the clutch 90 is again disposedin its inoperative or disconnected position and the friction wheel 102is also held away from the drive belts 56 so that the jack shaft 100will not be driven. In this mode the flexible power line 98 is stillconnected to the main drive shaft through belt 94 and therefore, thegrinding wheel will be caused to rotate when the output shaft 50 ofgearbox 44 is caused to rotate. In order to grind the second bevel 78means are provided to hold the grinding means along a radial innersurface of each knife. These means include guide pins 114 which aredisposed in such a manner as to be direction. To achievereversedirection rotation, the

clutch 90 is shifted from .its clutching position, shown in FIG. 10, toits disengaged position, shown in FIG. 11. Jack shaft 100 is then drivenby engaging the friction wheel 102 with the belt drive 56 as it passesover sheave 58. The jack shaft, which is now rotating in the directionof the arrow 103, will drive the cutterhead 38 in a reverse direction,as the shaft 88 is driven through belt 104 which passes over sheave 106on the jack shaft and 108 onthe cutterhead drive shaft. It should benoted at this point that a belt 104 is always disposed over sheaves 106and 108, and in the mode of operation illustrated in- FIG. 10, it willcause the jack shaft 100 to rotate in the direction indicated by thearrow 110. As the cutterhead is being rotated in its reverse directionas shown in FIG. 1 1', it is necessary to move the grinding means 79back and forth across the width of the'cutterhead to grind the leadingedge along the length of each knife. To this end, handle means 86 isprovided which can be manually engaged to move the grinding means backand forth across the width of the engageable with the leading edge ofeach knife 72 and means operable to bias each knife stays in engagementwith the guide means as the grinding means are moved back and forthacross the width of the cutterhead. The biasing means, indicatedgenerally at 116, include a rod 118 engageable with the cutterhead andprojecting laterally outwardly therefrom when in its engaged position,and a spring 120 engageable with one end of the rod 118 and operable tobias the cutterhead in a forward direction. When the grinding means isdisposed in its inoperativeposition (FIG. 10) or in its first mode (FIG.11) the guide pins 114 and the biasing means 116 are disposed in aninoperative position.

DETAILS OF THE POWER KNIFE GRINDER tails of the power knife grinder 79will be more fully described. The grinding means 79 includes a carriageor carrier 122 which is supported at one end on a fixed cylindricalshaft 124 and, atthe other end, on a moveable cylindrical shaft 125. Thefixed shaft 124 is mounted on and extends between a left and right sidesheets 14, 16, respectively, as can best be seen from FIG. 3. Themovable shaft 125 is supported formovement towards and away from therotatable cutterhead 38 by the moving means 84 in a manner more fullyset forth below. The carriage 122 has a yoke portion 126 slideablydisposed to either side of the fixed shaft 124, as can best be seen inFIGS. 8 and 9. The rotary .abrasive wheel is rotatably supported on thecarriage 122 between the fixed and movable shaft 124, 125. As themovable shaft is moved towards and away from the periphery of thecutterhead the abrasive wheel will move in and out of grindingrelationship with the knives of the cutterhead.

The fixed shaft 124 is mounted between the walls 14 and 16 by left andright brackets 128, 130, respectively, (FIGS. 2 and 3). The brackets arewelded to the shaft 124 and are bolted to the walls 14, 16, by bolts132.

The shaft 124 is positioned-rearwardly of the movable shaft 125. Thewalls 14 and 16 have openings 134 The opposite ends of the adjustablecylindrical shaft 125 are provided with threaded apertures which re- 7ceive threaded shafts 136, 138. A rigid frame, indicated generally at140, supports the threaded shafts 136, 138

and comprises a hollow cylindrical tubular cross beam 142 extending tothe outer sides of the walls 14, 16, the beam carrying bar like mountingmembers 144, 146 extending perpendicularly to the cross beam 142 and inwardly towards the cutterhead 38. The beam 142 is welded to the sidewalls 14, 16 and the mounting members 144, 146 are welded to the beam.The mounting members 144, 146 have longitudinally extending openings148, 150 through which the ends of the adjustable cylindrical shaft 125extend. The threaded shafts 136, 138 are rotatably mounted in the spacedapart brackets 152, 154, 156, 158 which'are welded to the bar likemembers 144, 146, the brackets extending away from the cutterhead 38.The threaded shafts are held against longitudinal movement by bevelgears 160, 162 and nuts 164, 166 which are pinned to the ends of therespective threaded shafts to' prevent relative rotation thereto. Theshafts 136, 138 therefore firmly hold the cylindrical adjustable shaft125 against lateral and longitudinal movement. The only movement of theadjustable shaft 125 is the linear movement along the threaded shafts asthese shafts are rotated to adjust the position of the abrasive wheel80. The threaded shaft 138 extends upward through the shield 168 (FIG.3) guarding the end of the knife sharpener. On the upper end of theshaft is a knobbed handle 170 for manually rotating the shaft. Thethreaded shaft 138 is connected to the threaded shaft 136 by a crossshaft 172 having beveled gears 174, 176 meshing with the beveled gears160, 162 mounted on the threaded shafts 136, 138, respectively. Thecross shaft 172 extends through the hollow cross beam 142 and isrotatably mounted in the bar like mounting members 144, 146. Thusrotational movement of the handle 170 on shaft 138 will impart equalrotational movement to shaft 136. The adjustable shaft is thus movedevenly inwardly and outwardly with respect to the cutterhead and is heldfirmly in position by the threaded shafts 136 and 138.

In the grinding operation of the first bevel the abrasive wheel 80 isindexed forwardly at the end of each pass by rotation of the handle 170for measuring the amount of inward movement of the abrasive wheel. Adetent, indicated generally at 178 (FIG. is mounted on the side of thebar like member 146 to indicate the movement of the adjusting means. Thedetent 178 comprises a base 180 with a bore 182 extending radially fromthe beveled gear 176', a pawl 184 pressed against the teeth of thebeveled gear 176 by a spring 186 compressed by a bolt 188 threaded intothe bore 182. As the gear 176 rotates an audible click occurs when thepawl recesses between the gear teeth. The inward movement can bedetermined from these clicks. Usually, the abrasive wheel 80 ispositioned by a single click for each pass of the abrasive wheel 80across the width of the cutterhead.

The threaded shaft 136, 138 are firmly held at each end and theadjustable shaft 125 moves in a plane passing through the cutterhead toimpart a linear movement to one end of the carrier 122. The other end ofthe carrier 122 rotates about the fixed shaft 124 as said one of thecarrier is adjusted, the yoke portion 126 also providing for a limitedsliding movement of the carrier 122 towards and away from the fixedshaft.

The abrasive wheel 80 is removably mounted on one end of the flexibledrive shaft 98 by the circular washers 190, 192 (FIG. 4) on oppositesides of the abrasive wheel. Bolt 194 fits in the center hole in theabrasive wheel and is threaded on the end of the drive shaft 98 tosecure the abrasive wheel thereto. The drive shaft 98 is rotatablymounted in the boss 196 of the carrier parallel to the adjusting shaftand the fixed shaft 124. The abrasive wheel can be replaced by theremoval of the bolt 194. The abrasive wheel is used until worn to aminimum diameter and is then replaced by a new wheel. Thus, in additionto the inward and outward movement of the abrasive wheel as it isadjusted, the abrasive wheel may change in diameter as it is worn andsubsequently replaced.

Another variable effecting relationship of the abrasive wheel withrespect to the knife is the diameter of the cutting cylinders. As thefirst bevel of the knives are constantly reground the diameter of thecutterhead will be reduced unless of course the knives are repositionedby loosening the knife holding stud 197 (FIG. 7) and moving the knifeoutwardly (to the left in FIG. 7) on the mounting blocks 198 which arein turn carried by the cutterhead. Thus, if the knife is not readjustedthe cutting edges will subscribed a cutting cylinder of reduceddiameter. In positioning the grinding means to cut the second bevel itis necessary that the guide pins 1 14 maintain a proper relationshipbetween the second bevel and the first bevel over the variousrelationships of cutterhead diameter and abrasive wheel diameter, andalso as the stone moves towards and away from the cutterhead as theadjusting means is adjusted to compensate for difference in the variousdiameters. To compensate for differences in the various diameters theguide pins 1 14 are angularly mounted on opposite sides of the abrasivewheel to maintain a carrier in the desired contact with a knife edge asthe carrier is moved from side to side along the length of each of theknives while sharpening the second bevel. The guide pins havecylindrical stem portions 200 (FIG. 6) with rollers 202 mounted on theends thereof, the rollers being adapted to roll along the knife edge.The mountings of the guide pins in the carrier are the same and adescription of the mounting of one guide pin will sufice for both. Thestem of each mounting pin 200 fits into a stepped bore 204. The lowerstepped portion 208 has a diameter slightly greater than the diameter ofthe stemmed portion 200 and is adapted to closely embrace the stemportion 200. The intermediate stepped portion 208 is larger and has anO-ring 210 at the bottom thereof which is pressed into holdingengagement with the stem portion 200 by sleeve 212. The sleeve 212 isforced into holding engagement by a nut 214 which is threaded into alarger bore portion 216, which is disposed on the'opposite side of thecarrier from the bore portion 206. The nut 216 has wing portions 218 formanual tightening of the guide pins into the socket.

Thus, as the nut is tightened the sleeve 212 will be forced intoengagement with the O-ring 210, compressing the O-ring into engagementwith the stem portion 200. In the full lines of FIG. 6, the guide pin isin guiding relationship with the knife edge. In the dot-dash position ofthat figure the guide pin is in its storage position. The guide pin willbe carried in the storage position except for grinding of the secondbevel.

In FIG. 9 a new abrasive wheel is shown which is at its largestdiameter. As can be seen from FIG. 9, the guide pins 1 14 are at anangle to the carrier. The rollers 202 on the guide pins are positionedto be intersected by a peripheral plane tangential to the grinding ofthe abrasive wheel when forming the second bevels. The guide pins are onopposite sides of the grinding wheel to engage sections of the knife oneither side of the wheel 80 to position the section of the knife betweenthe guide pins in proper grinding contact with the abrasive wheel as canbe seen from FIGS. 3 and 9.

CUTTERIIEAD CLUTCH As has previously been noted from the summary ofoperation of the various modes of the knife grinder, it is necessary todisconnect the main drive to the cutterhead 38 through the'operation ofa clutch indicated generally at 90. This clutch consists of a firstfixed clutch member 220 (FIG. 3) rigidly secured to the main drive shaft52 to theright of sheave 94, the fixed clutch member being provided withspaced apart apertures 222. A second clutch member 224 is rigidlysecured to the cutterhead drive shaft 88. The cutterhead drive shaft isnot drivingly connected to the main drive shaft 52 except through theclutch 90. The second clutch member carries shiftable dogs 226 which maybe disposed in the apertures 222 in the first clutch member 220 toeffect a drivingly relationship between the first and second clutchmembers 220, 224, respectively. In order to move the dogs from theirclutching position to their disengaged position it is necessary towithdraw the dogs 226 from the apertures 222. To this end rods 228 areprovided, the rods being mounted in the right hand end of the dogs 226and manually engageable to shift the dogs from their left hand clutchingposition, shown in FIG. 3, to their right hand disengaged position. Eachof the rods 228 is biased inwardly towards the cutterhead drive shaft 88by spring means not shown, and when shifting from the clutching positionto the disengaged position, the rods 228 are first shifted outwardlyagainst the spring pressure, and then I moved to the right over lugs 230until they are past the lugs at which point the rods are releasedagainst the spring pressure, thespring pressure then holding the pins intheir disengaged positions and not permitting accidental insertion ofthe pins into the corresponding apertures 222. The left-hand end of the'cutterhead drive shaft 88 is provided with a pilot member (not shown)which is received by a pilot bore (also not shown) in the main driveshaft 52, the pilot holding the shafts 88 and 52 in axial alignment.

CUTTERI-IEAD REVERSE DRIVE The manner in which the friction wheel 100 ismoved into and out of disengagement with the belt drive 56 is notmaterial to this invention, however, it should suffice to note that anover center linkage arrangement is provided, this linkage arrangement isprovided, this POWER KNIFE GRINDER DRIVE The driving end of the flexibledrive shaft 98 is carried on a pivoted L-shaped lever 232 (FIGS. 2 and3) and lower portion being generally parallel to the drive 10 sheaves 52and 88 and mounted on spaced apart brackets 234 secured to and extendingforwardly from the rear transverse frame member 18. A spring 236normally biases the upper portion of the lever, which carries a handle238, rearwardly towards frame member 18. The intermediate portion of thelever 232 is provided with bracket means, one end of which 240 isconnected to the spring 236, and the other end of which supports thesheave 96 and the sheath 242 of the flexible drive line 98. To connectthe disconnectable drive 82, it is necessary to shift the belt 92 fromits storage position, shown in broken lines in FIG. 3, to its driveposition, shown in full lines in FIG.'3. In the storage position one endof the belt is disposed over the flexible drive line 98, and anotherover a stud 244 carried by a portion of the forage harvester frame. Asthe spring biases the handle 238 rearwardly the belt will be held in atension position when its in its storage position and will not shift outof its storage position. To move the belt into its driving position thehandle 238 is pushed forwardly and one end of the belt is disposed overthe sheave 94, and the other end is disposed over the sheave 96. Thehandle isthen released, and the spring will then hold the belt in itsproper driving tension. Therefore, the drive to the grinding means canreadily beestablished and disconnected.

CUTTERHEAD BIASING MEANS Finally, reference was made in the descriptionof the operation of this device to the cutterhead biasing means. As thisdevice is only schmetically illustratedin FIGS. 10, 11 and 12, referenceis now directed to FIG. 2. This figure shows the biasirig'device in itsstorage position in full line and in its normal operative biasing p0sition in phanton lines. In the storage position one end of the rod 118is disposed within an aperture in the frame of the forage harvester, thespring then beiiig in I a more or less retracted position. In itsbiasing position,

shown in phantom, the rod is inserted into one of a plurality of spacedapart apertures 244 in the cutterhead, the rod passing through anarcuate slot 246 in the side sheet 16. In actual practice the cutterheadof the forage harvester is provided with at least 24 spaced apartapertures 244 so that any of the knives mounted on the forage harvestercan be advantageously positioned for grinding of the second bevel. Whenthe rod is disposed in the aperture, the spring is somewhat tensioned ascan be seen best from FIG. 2.

CONCLUSION which is utilized to cut both bevels provides a fastergrinding of the first bevel then is conventionally accomplished with astationary stone. Furthermore, it should be noted that this powergrinder requires very little maintenance, and when necessary, thegrinding wheel can be very easily replaced.

While the preferred structure in which the principles of the presentinvention have been incorporated is shown and described above, itis tobe understood that the invention is not to be limited to the particulardetails, shown and described above, but that, in fact, widely differentmeans may be employed in the practice of the broader aspects of theinvention.

Having thus described our invention what we claim l. A method ofgrinding first and second bevels on the knives of a forage harvestercutterhead while the knives are mounted on the cutterhead with a singlegrinding means mounted on the forage harvester comprising steps of:

A. connecting a drive to the cutterhead and rotating the cutterhead;

B. advancing the grinding means into engagement with the radial outerperiphery of the rotating cutterhead; v

C. moving the grinding means back and forth along the length of therotating knives to grind the radial outer periphery of the knives;

D. repeating the advancing and moving steps until a satisfactory firstbevel is ground on the radial outer periphery of the knives of therotating cutterhead;

E. disconnecting said drive to the cutterhead and disposing thecutterhead in a free-wheeling mode;

F. advancing said grinding means into engagement with one of the knivesand a location spaced slightly inwardly of the first bevel;

G. moving said grinding means back and forth along the length of saidone knife to grind a second bevel;

H. repeating the advancing and moving steps F and G until a satisfactorysecond bevel is ground on said one knife; and i I. repeating steps F, Gand H with each of the other knives on the cutterhead until asatisfactory second bevel is ground on all the knives.

2. The method of claim 1 further characterized by the steps of:

J. providing the grinding means with a guaging means engageable withthe. leading edge of one of the knives, and

K. biasing the leading edge of each knife being ground into engagementwith the guaging means during steps F and G of Claim 1.

3. The method of claim 1 wherein the single grinding means is arotatable abrasive member, further characterized by the steps of:

L. rotating the abrasive member.

4. A knife grinder for a forage harvester of the type having a frame, ashear bar mounted on the frame, a rotatable cutterhead mounted on theframe, said cutterhead carrying a plurality of knives which cooperatewith the shear bar upon forward rotation of the cutterhead to cut cropmaterial conveyed past the shear bar, said knife grinder comprising:

grinding means mounted on the frame of the forage harvester adjacent thesaid cutterhead at a location spaced outwardly of the periphery of thecutterhead;

means operable to move said grinding means towards and away from saidcutterhead to dispose the grinding means in either a first grindingposition for cutting a first bevel on the knives of the rotatablecutterhead, a second grinding position for cutting a second bevel on theknives of the cutterhead, or

in a third inoperative position spaced radially outwardly of saidcutterhead;

means operable to move said grinding means back and forth across thewidth of the cutterhead when said grinding means is disposed in eitherof the said first or second positions;

drive means operable to rotate said cutterhead whereby a first bevel canbe ground on the outer periphery of the knives as the knives rotate pastthe grinding means when the grinding means is disposed in its firstposition and as the grinding means is moved back and forth across thewidth of the cutterhead;

means operable to disconnect the cutterhead drive means to permit thecutterhead to free-wheel; and

means operable to hold the grinding means along a radially inner surfaceof each of the knives when the grinding means is disposed in the secondgrinding position whereby a second bevel can be ground on the knivesradially inwardly of the first bevel as the grinding means is moved backand forth across the width of the cutterhead.

5. A knife grinder as set forth in claim 4, wherein the grinding meansis provided with guide pins engageable 8. A knife grinder as set forthin claim 4, wherein said grinding means includes a rotatable abrasivegrinding wheel mounted on an axis parallel to the axis of rotation ofthe cutterhead.

9. A knife grinder as set forth in claim 4, wherein said grinding meansincludes a carriage mounted for movement parallel to the axis ofrotation of said cutterhead, and the means operable to move saidgrinding means back and forth across the width of-the cutterheadincludes a manually engageable handle projecting outwardly of the frameof the forage harvester, said handle being connected to said carriage.

10. A knife grinder as set forth in claim 9, wherein said grinding meanscomprises a rotary abrasive member mounted on said carriage androtatable about an axis parallel to the axis of rotation of saidcutterhead.

11. A knife grinder as set forth in claim 4, wherein the cutterheaddrive means rotates said cutterhead in a rearward direction during thegrinding of the first bevel.

12. In combination with a forage harvester of the type having a frameadapted to be propelled forwardly over a field of crop bearing material,a shear bar mounted on said frame, "a rotatable cutterhead mounted forrotation about a generally transverse axis and having a plurality ofknives mounted on its radial outer periphery, drive means operable torotate said cutterhead in a forward direction whereby crop mate rialconveyed past said shear bar will be cut by said knives during forwardrotation of said cutterhead; a powered knife grinder comprising grindingmeans mounted on the frame adjacent the periphery of said cutterhead;means operable to move said grinding means towards and away from saidcutterhead between an inoperative grinding position, through a firstgrinding position wherein said grinding means can grind a first bevel onthe knives of said cutterhead, and to a second grinding position whereinsaid grinding means can grind a second bevel on the knives mounted onsaid cutterhead; means operable to move said abrasive structure back andforth across the width of said cutterhead when said grinding means isdisposed in its first grinding position; whereby a first bevel can becut on said cutterhead knives during rotation of said cutterhead, clutchmeans operable to disconnect said cutterhead from said cutterhead drivemeans; and means operable to hold the grinding means along a radialinner surface of each of the knives when said clutch means isdisconnected and said knife is disposed in its second parallel to theaxis of said cutterhead, and further characterized by the provision ofdrive means interconnecting said rotatable abrasive structure with saidforage harvester cutterhead drive means.

14. The combination set forth in claim 13, wherein said drive means forthe rotatable abrasive structure is disconnectable from the drive meansof the forage harvester cutterhead whereby the forage harvestercutterhead may be rotated to cut crop material conveyed past said shearbar without rotation of said rotary abrasive structure.

15. The combinations set forth in claim 12, wherein the means operableto hold'the grinding means along a radial inner surface comprises guidepins carried by and movable with the grinding means, and biasing meansoperable to bias the leading edge of each of the knives into engagementwith said guide means when said clutch means is disconnected.

16; A method of grinding second bevels on the knives of a forageharvester cutterhead while the knives are mounted on the cutterhead witha grinding means mounted on the forage harvester, said knives beingprovided with a first bevel, comprising steps of:

A. disposing the cutterhead in a free-wheeling mode;

B. providing the grinding means with a gauging means engageable with theleading edge of one of the knives;

C. advancing said grinding means into engagement with one of the knivesat a location spaced slightly inwardly of the first bevel and biasingthe leading edge of said one knife to be ground into engagement with thegauging means;

D. moving said grinding means back and forth along the length of saidone knife to grind asecond bevel while the leading edge of said knife iscontinuously biased into engagement with said gauging means;

E. repeating the advancing and moving steps C and D until a satisfactorysecond bevel is ground on said one knife; and

F repeating steps C, D and E with each of the other knives on thecutterhead until a satisfactory second bevel is ground on all theknives.

17. The method of claim 16 wherein the single grinding means is arotatable abrasive member, further characterized by the steps of:

G. rotating the abrasive member.

18. A knife grinder for a forage harvester of the type having a frame, ashear bar mounted on the frame, a rotatable cutterhead mounted ontheframe, said cutterhead carrying a plurality of knives which cooperatedwith the shear bar upon forward rotation of the cutterhead to cut cropmaterial conveyed past the shear bar, said knives having first andsecond bevels, said knife grinder comprising:

grinding means mounted on the frame of the forage harvester adjacent thecutterhead at a location spaced outwardly of the periphery of thecutterhead;

means operable to move said grinding means towards and away from saidcutterhead to dispose the grinding means in either a grinding positionfor regrinding second bevel on the knives of the cutterhead, or in aninoperative position spaced radially outwardly of said cutterhead;

means operable to move said grinding means back and forth across thewidth of the cutterhead when said grinding means is disposed in saidgrinding position; and

means operable to hold the grinding means along a radially inner surfaceof each of the knives when the grinding means is disposed in thegrinding position whereby the second bevel can be regroundon the knivesradially inwardly of the first bevel as the grinding means is moved backand forth across the width of the cutterhead.

19. A knife grinder as set forth in claim 18, wherein the grinding meansis provided with guide pins engageable with the leading edge of eachknife during the grinding of the second bevel.

20. A knife grinder as set forth in claim 19, wherein spring means areprovided to bias the leading edge of each knife into engagement withsaid guide pins.

21. A knife grinder as set forth in claim 18, wherein said grindingmeans includes a rotatable abrasive grinding wheel mounted on an axisparallel to the axis of rotation of the cutterhead.

22. In combination with a forage harvester of the type having a frameadapted to be propelled forwardly over a field of crop bearing material,a shear bar mounted on said frame, a rotatable cutterhead mounted forrotation about a generally transverse axis and having a plurality ofknives mounted on its radial outer periphery, drive means includingclutch means movable between engaged and disengaged positions andoperable to rotate said cutterhead in a forward direction when saidclutch means is in its engaged position whereby crop material conveyedpast said shear bar will be cut by said knives during forward rotationof said cutterhead; a powered knife grinder comprising grinding meansmounted on the frame adjacent the periphery of said cutterhead; meansoperable to move said grinding means towards and away from saidcutterhead between an operative grinding position and an inoperativegrinding position, means operable to hold the grinding means along aradial inner surface of each of the knives when said clutch means is inits disengaged 15 position and said grinding means is disposed in itsgrinding position, and means operable to move said grinding means backand forth across the width of the cutterhead whereby a second bevel canbe reground on each of the knives.

23. The combination set forth in claim 22, wherein said grinding meanscomprises a rotatable abrasive structure mounted for rotation about anaxis generally parallel to the axis of said cutterhead, and furthercharacterized by the provision of drive means interconnecting saidrotatable abrasive structure with said forage harvester cutterhead drivemeans.

24. The combination set forth in claim 22, wherein the means operable tohold the grinding means along a radial inner surface comprises guidepins carried by and movable with the grinding means, and biasing meansoperable to bias the leading edge of each of the knives into engagementwith said guide means when said clutch means is disconnected.

25. A knife sharpener-for a forage harvester having a rotatablecutterhead with knives and comprising an abrasive wheel for grindingrelief bevels of said knives,

an adjustable support means for rotatably supporting said abrasive wheeland moving said wheel inwardly and outwardly from said cutterheadbetween operative and inoperative positions,

guide means on said adjustable support means for engaging the cuttingedge of a knife, said guide means positioning the knife in relation tosaid wheel, and said guide means being spaced and angled in relation tosaid abrasive wheel to position said engaged knife and the abrasivewheel ina substantially constant relation to one another for grindingrelief bevels over the changes in the position and diameter of theabrasive wheel, and

means operable to move said support means back and forth across thewidth of the cutterhead when said abrasive wheel is disposed in itsoperative position.

26. A knife sharpener as set forth in claim 25 wherein each of saidguide means has a mounting portion and a knife engaging portion. I

27. A knife sharpener as set forth in claim 26 wherein said knifeengaging portions are sleeves rotatably mounted on said mountingportion.

28. A knife sharpener as set forth in claim 25 wherein said guide meansare on opposite sides of said abrasive wheel whereby at least one pin ismaintained in engagement with the knife being ground as the adjustablesupport is moved back and forth across the width of the cutterhead.

29. In a forage harvester having a housing with spaced vertical sidewalls forming a comminuting chamber,

a cutterhead rotatably mounted in said chamber between said walls,

a plurality of longitudinally extending circumferentially arrangedknives mounted on said cutterhead and subscribing a cutting cylinder onrotation of said cutterhead, and

a shear bar mounted on said housing parallel to and adjacent the cuttingcylinder in cooperative relation with said knives for chopping cropmaterial;

a knife sharpener comprising an abrasive wheel, carrier means rotatablysupporting said abrasive wheel, drive means connected to said abrasivewheel, shaft-like means having a fixed axis and pivotally supportingsaid carrier,

an adjustable shaft mounted in said carrier means on the other side ofsaid abrasive wheel from said shaft-like means,

an adjusting mechanism coupled to said adjustable shaft for moving saidadjustable shaft, carrier means and abrasive wheel toward and away fromsaid cutterhead to move said abrasive wheel to grind bevels on saidknives of said cutterhead,

guide pins positionable to extend from said carrier means towards saidcutterhead for engagement by one of said knives to position said engagedknife and said abrasive wheel in a substantially constant relation toone another for grinding a relief bevel therein over the changes in theposition and diameter of said abrasive wheel.

30. A method of grinding firstand second bevels on the knives of aforage harvester cutterhead while the knives are mounted on thecutterhead with a single grinding means mounted on the forage harvestercomprising steps of: A. connecting a drive to the cutterhead androtating the cutterhead; v B. advancing the grinding means intoengagement with the radial outer periphery of the rotating cutterhead; VC. moving the grinding means back and forth along the length of therotating knives to grind the radial outer periphery of the knives; D.repeating the advancing and moving steps until a satisfactory firstbevel is ground on the radial outer periphery of the knives of therotating cutterhead;

H. repeating the advancing and moving steps F and G until a satisfactorysecond bevel is ground on said one knife; and

l. repeating steps F, G andH with each of the other knives on thecutterhead until a satisfactory second bevel is ground on all theknives.

* a: a: s:

1. A method of grinding first and second bevels on the knives of aforage harvester cutterhead while the knives are mounted on thecutterhead with a single grinding means mounted on the forage harvestercomprising steps of: A. connecting a drive to the cutterhead androtating the cutterhead; B. advancing the grinding means into engagementwith the radial outer periphery of the rotating cutterhead; C. movingthe grinding means back and forth along the length of the rotatingknives to grind the radial outer periphery of the knives; D. repeatingthe advancing and moving steps until a satisfactory first bevel isground on the radial outer periphery of the knives of the rotatingcutterhead; E. disconnecting said drive to the cutterhead and disposingthe cutterhead in a free-wheeling mode; F. advancing said grinding meansinto engagement with one of the knives and a location spaced slightlyinwardly of the first bevel; G. moving said grinding means back andforth along the length of said one knife to grind a second bevel; H.repeating the advancing and moving steps F and G until a satisfactorysecond bevel is ground on said one knife; and I. repeating steps F, Gand H with each of the other knives on the cutterhead until asatisfactory second bevel is ground on all the knives.
 2. The method ofclaim 1 further characterized by the steps of: J. providing the grindingmeans with a guaging means engageable with the leading edge of one ofthe knives, and K. biasing the leading edge of each knife being groundinto engagement with the guaging means during steps F and G of Claim 3.The method of claim 1 wherein the single grinding means is a rotatableabrasive member, further characterized by the steps of: L. rotating theabrasive member.
 4. A knife grinder for a forage harvester of the typehaving a frame, a shear bar mounted on the frame, a rotatable cutterheadmounted on the frame, said cutterhead carrying a plurality of kniveswhich cooperate with the shear bar upon forward rotation of thecutterhead to cut crop material conveyed past the shear bar, said knifegrinder comprising: grinding means mounted on the frame of the forageharvester adjacent the said cutterhead at a location spaced outwardly ofthe periphery of the cutterhead; means operable to move said grindingmeans towards and away from said cutterhead to dispose the grindingmeans in either a first grinding position for cutting a first bevel onthe knives of the rotatable cutterhead, a second grinding position forcutting a second bevel on the knives of the cutterhead, or in a thirdinoperative position spaced radially outwardly of said cutterhead; meansoperable to move said grinding means back and forth across the width ofthe cutterhead when said grinding means is disposed in either of thesaid first or second positions; drive means operable to rotate saidcutterhead whereby a first bevel can be ground on the outer periphery ofthe knives as the knives rotate past the grinding means when thegrinding means is disposed in its first position and as the grindingmeans is moved back and forth across the width of the cutterhead; meansoperable to disconnect the cutterhead drive means to permit thecutterhead to free-wheel; and means operable to hold the grinding meansalong a radially inner surface of each of the knives when the grindinGmeans is disposed in the second grinding position whereby a second bevelcan be ground on the knives radially inwardly of the first bevel as thegrinding means is moved back and forth across the width of thecutterhead.
 5. A knife grinder as set forth in claim 4, wherein thegrinding means is provided with guide pins engageable with the leadingedge of each knife during the grinding of the second bevel.
 6. A knifegrinder as set forth in claim 5, wherein spring means are provided tobias the leading edge of each knife into engagement with said guidepins.
 7. A knife grinder as set forth in claim 4, wherein each knife ismounted on the periphery of the cutterhead at an angle to the radius ofthe cutterhead, the first bevel being ground on a tangent to thecutterhead.
 8. A knife grinder as set forth in claim 4, wherein saidgrinding means includes a rotatable abrasive grinding wheel mounted onan axis parallel to the axis of rotation of the cutterhead.
 9. A knifegrinder as set forth in claim 4, wherein said grinding means includes acarriage mounted for movement parallel to the axis of rotation of saidcutterhead, and the means operable to move said grinding means back andforth across the width of the cutterhead includes a manually engageablehandle projecting outwardly of the frame of the forage harvester, saidhandle being connected to said carriage.
 10. A knife grinder as setforth in claim 9, wherein said grinding means comprises a rotaryabrasive member mounted on said carriage and rotatable about an axisparallel to the axis of rotation of said cutterhead.
 11. A knife grinderas set forth in claim 4, wherein the cutterhead drive means rotates saidcutterhead in a rearward direction during the grinding of the firstbevel.
 12. In combination with a forage harvester of the type having aframe adapted to be propelled forwardly over a field of crop bearingmaterial, a shear bar mounted on said frame, a rotatable cutterheadmounted for rotation about a generally transverse axis and having aplurality of knives mounted on its radial outer periphery, drive meansoperable to rotate said cutterhead in a forward direction whereby cropmaterial conveyed past said shear bar will be cut by said knives duringforward rotation of said cutterhead; a powered knife grinder comprisinggrinding means mounted on the frame adjacent the periphery of saidcutterhead; means operable to move said grinding means towards and awayfrom said cutterhead between an inoperative grinding position, through afirst grinding position wherein said grinding means can grind a firstbevel on the knives of said cutterhead, and to a second grindingposition wherein said grinding means can grind a second bevel on theknives mounted on said cutterhead; means operable to move said abrasivestructure back and forth across the width of said cutterhead when saidgrinding means is disposed in its first grinding position; whereby afirst bevel can be cut on said cutterhead knives during rotation of saidcutterhead, clutch means operable to disconnect said cutterhead fromsaid cutterhead drive means; and means operable to hold the grindingmeans along a radial inner surface of each of the knives when saidclutch means is disconnected and said knife is disposed in its secondgrinding position whereby a second bevel can be ground on each of theknives radially inwardly of the first bevel as the grinding means ismoved back and forth across the width of the cutterhead.
 13. Thecombination set forth in claim 12, wherein said grinding means comprisesa rotatable abrasive structure mounted for rotation about an axisgenerally parallel to the axis of said cutterhead, and furthercharacterized by the provision of drive means interconnecting saidrotatable abrasive structure with said forage harvester cutterhead drivemeans.
 14. The combination set forth in claim 13, wherein said drivemeans for the rotatable abrasive structure is disconnectable from thedrive means of the forage harvester cutterhead wherEby the forageharvester cutterhead may be rotated to cut crop material conveyed pastsaid shear bar without rotation of said rotary abrasive structure. 15.The combinations set forth in claim 12, wherein the means operable tohold the grinding means along a radial inner surface comprises guidepins carried by and movable with the grinding means, and biasing meansoperable to bias the leading edge of each of the knives into engagementwith said guide means when said clutch means is disconnected.
 16. Amethod of grinding second bevels on the knives of a forage harvestercutterhead while the knives are mounted on the cutterhead with agrinding means mounted on the forage harvester, said knives beingprovided with a first bevel, comprising steps of: A. disposing thecutterhead in a free-wheeling mode; B. providing the grinding means witha gauging means engageable with the leading edge of one of the knives;C. advancing said grinding means into engagement with one of the knivesat a location spaced slightly inwardly of the first bevel and biasingthe leading edge of said one knife to be ground into engagement with thegauging means; D. moving said grinding means back and forth along thelength of said one knife to grind a second bevel while the leading edgeof said knife is continuously biased into engagement with said gaugingmeans; E. repeating the advancing and moving steps C and D until asatisfactory second bevel is ground on said one knife; and F. repeatingsteps C, D and E with each of the other knives on the cutterhead until asatisfactory second bevel is ground on all the knives.
 17. The method ofclaim 16 wherein the single grinding means is a rotatable abrasivemember, further characterized by the steps of: G. rotating the abrasivemember.
 18. A knife grinder for a forage harvester of the type having aframe, a shear bar mounted on the frame, a rotatable cutterhead mountedon the frame, said cutterhead carrying a plurality of knives whichcooperated with the shear bar upon forward rotation of the cutterhead tocut crop material conveyed past the shear bar, said knives having firstand second bevels, said knife grinder comprising: grinding means mountedon the frame of the forage harvester adjacent the cutterhead at alocation spaced outwardly of the periphery of the cutterhead; meansoperable to move said grinding means towards and away from saidcutterhead to dispose the grinding means in either a grinding positionfor regrinding second bevel on the knives of the cutterhead, or in aninoperative position spaced radially outwardly of said cutterhead; meansoperable to move said grinding means back and forth across the width ofthe cutterhead when said grinding means is disposed in said grindingposition; and means operable to hold the grinding means along a radiallyinner surface of each of the knives when the grinding means is disposedin the grinding position whereby the second bevel can be reground on theknives radially inwardly of the first bevel as the grinding means ismoved back and forth across the width of the cutterhead.
 19. A knifegrinder as set forth in claim 18, wherein the grinding means is providedwith guide pins engageable with the leading edge of each knife duringthe grinding of the second bevel.
 20. A knife grinder as set forth inclaim 19, wherein spring means are provided to bias the leading edge ofeach knife into engagement with said guide pins.
 21. A knife grinder asset forth in claim 18, wherein said grinding means includes a rotatableabrasive grinding wheel mounted on an axis parallel to the axis ofrotation of the cutterhead.
 22. In combination with a forage harvesterof the type having a frame adapted to be propelled forwardly over afield of crop bearing material, a shear bar mounted on said frame, arotatable cutterhead mounted for rotation about a generally transverseaxis and having a plurality of knives mounted on its radial outerperiphery, drive means including clutch means movable between engagedand disengaged positions and operable to rotate said cutterhead in aforward direction when said clutch means is in its engaged positionwhereby crop material conveyed past said shear bar will be cut by saidknives during forward rotation of said cutterhead; a powered knifegrinder comprising grinding means mounted on the frame adjacent theperiphery of said cutterhead; means operable to move said grinding meanstowards and away from said cutterhead between an operative grindingposition and an inoperative grinding position, means operable to holdthe grinding means along a radial inner surface of each of the kniveswhen said clutch means is in its disengaged position and said grindingmeans is disposed in its grinding position, and means operable to movesaid grinding means back and forth across the width of the cutterheadwhereby a second bevel can be reground on each of the knives.
 23. Thecombination set forth in claim 22, wherein said grinding means comprisesa rotatable abrasive structure mounted for rotation about an axisgenerally parallel to the axis of said cutterhead, and furthercharacterized by the provision of drive means interconnecting saidrotatable abrasive structure with said forage harvester cutterhead drivemeans.
 24. The combination set forth in claim 22, wherein the meansoperable to hold the grinding means along a radial inner surfacecomprises guide pins carried by and movable with the grinding means, andbiasing means operable to bias the leading edge of each of the knivesinto engagement with said guide means when said clutch means isdisconnected.
 25. A knife sharpener for a forage harvester having arotatable cutterhead with knives and comprising an abrasive wheel forgrinding relief bevels of said knives, an adjustable support means forrotatably supporting said abrasive wheel and moving said wheel inwardlyand outwardly from said cutterhead between operative and inoperativepositions, guide means on said adjustable support means for engaging thecutting edge of a knife, said guide means positioning the knife inrelation to said wheel, and said guide means being spaced and angled inrelation to said abrasive wheel to position said engaged knife and theabrasive wheel in a substantially constant relation to one another forgrinding relief bevels over the changes in the position and diameter ofthe abrasive wheel, and means operable to move said support means backand forth across the width of the cutterhead when said abrasive wheel isdisposed in its operative position.
 26. A knife sharpener as set forthin claim 25 wherein each of said guide means has a mounting portion anda knife engaging portion.
 27. A knife sharpener as set forth in claim 26wherein said knife engaging portions are sleeves rotatably mounted onsaid mounting portion.
 28. A knife sharpener as set forth in claim 25wherein said guide means are on opposite sides of said abrasive wheelwhereby at least one pin is maintained in engagement with the knifebeing ground as the adjustable support is moved back and forth acrossthe width of the cutterhead.
 29. In a forage harvester having a housingwith spaced vertical side walls forming a comminuting chamber, acutterhead rotatably mounted in said chamber between said walls, aplurality of longitudinally extending circumferentially arranged knivesmounted on said cutterhead and subscribing a cutting cylinder onrotation of said cutterhead, and a shear bar mounted on said housingparallel to and adjacent the cutting cylinder in cooperative relationwith said knives for chopping crop material; a knife sharpenercomprising an abrasive wheel, carrier means rotatably supporting saidabrasive wheel, drive means connected to said abrasive wheel, shaft-likemeans having a fixed axis and pivotally supporting said carrier, anadjustable shaft mounted in said carrier means on the other sIde of saidabrasive wheel from said shaft-like means, an adjusting mechanismcoupled to said adjustable shaft for moving said adjustable shaft,carrier means and abrasive wheel toward and away from said cutterhead tomove said abrasive wheel to grind bevels on said knives of saidcutterhead, guide pins positionable to extend from said carrier meanstowards said cutterhead for engagement by one of said knives to positionsaid engaged knife and said abrasive wheel in a substantially constantrelation to one another for grinding a relief bevel therein over thechanges in the position and diameter of said abrasive wheel.
 30. Amethod of grinding first and second bevels on the knives of a forageharvester cutterhead while the knives are mounted on the cutterhead witha single grinding means mounted on the forage harvester comprising stepsof: A. connecting a drive to the cutterhead and rotating the cutterhead;B. advancing the grinding means into engagement with the radial outerperiphery of the rotating cutterhead; C. moving the grinding means backand forth along the length of the rotating knives to grind the radialouter periphery of the knives; D. repeating the advancing and movingsteps until a satisfactory first bevel is ground on the radial outerperiphery of the knives of the rotating cutterhead; E. disconnectingsaid drive to the cutterhead and disposing the cutterhead in afree-wheeling mode; F. advancing said grinding means into engagementwith one of the knives at a location spaced slightly inwardly of thefirst bevel; G. moving said grinding means back and forth along thelength of said one knife to grind a second bevel; H. repeating theadvancing and moving steps F and G until a satisfactory second bevel isground on said one knife; and I. repeating steps F, G and H with each ofthe other knives on the cutterhead until a satisfactory second bevel isground on all the knives.